When we bought our 5th wheel we put 1k down with the option that if we didn't like what we saw during the PDI to have that money refunded which was put in writing.
We were not ask for any money till we did our PDI which took over 4 hours, we only found two minor things wrong at the time an they were fixed before signing any papers the same day ...
I would say not doing a PDI is like gambling with a large about of money, would you lay down forty, fifty, sixty or more dollars on a **** table an roll the dice, your a fool if you do so or just have way to much money an don't care if you loose such ...
You see it all the time on this refectors/forms complaining how bad a product is an all the problems they are having, when ask if they did a PDI they say either no or the sales people stated it was already done ...
Safe travels